merge YARN-1229 from trunk. Define constraints on Auxiliary Service names. Change ShuffleHandler service name from mapreduce.shuffle to mapreduce_shuffle. Contributed by Xuan Gong.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1526066 13f79535-47bb-0310-9956-ffa450edef68